I would recommend taking Atlas to a veterinarian since he may need antibiotics especially with the kind of nasal discharge he is having. At the veterinarian they will also listen to his lungs to make sure they are clear and he doesn't have bronchitis or starting with pneumonia.
I would also recommend not having him be around other dogs until he is feeling much better.
I hope Atlas feels better soon and thank you for using Petco Pet Education Center, formerly Petcoach.